I have featured the SSB network and the Patchwork client before in a YouTube and LBRY video. It is a peer-to-peer (no central servers) social network built on an open protocol so there are many client apps for desktop as well as mobile, and the protocol is not owned by anyone.
Planetary has come up with an excellent iOS app (others to follow) that allows you to connect to this network, but you are not locked in to only using their app. It is privacy respecting, so no personal data is required to register and there is no advertising. Private posts are end-to-end encrypted whilst public posts are public and relayed via other users' devices (peers).
Planetary has added some additional features on top and these likely only work with other Planetary users such as keeping some posts back for users who have subscribed and pay for your content. To this end Planetary have also created a SSB pub of their own which allows Planetary users to find each other easily.
Anyone can follow anyone else across SSB but if you block someone then you don't see their posts, nor do you forward any of their posts any more. There is no moderation as you decide for yourself who you follow or interact with. There are no algorithms.
Planetary is an open, humane and decentralized social network that respects your privacy and honors makers and creators.